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The Case for Trees Continues: San Antonio Ranked 23rd worst for high ozone days.

The San Antonio area saw our first triple-digit day on June 16th. According to the National Weather Service (NWS), the temperature on June 16th was 101 degrees with a heat index of 115 degrees. As of the 16th “Excessive Heat Warning” has been instated. The NWS forecast this summer is that our area will experience one of the hottest and driest summers on record- again. According to, since the beginning of June, the San Antonio area has only had five days of considered “Good” quality air. The more trees we lose, the hotter and more polluted our communities will become.

The American Lung Association’s recently conducted their “State of the Air Report,” and found San Antonio ranked 23rd worst for high ozone days out of 227 metropolitan areas. Each city includes all the counties that form the economic and transportation network that makes up the metropolitan area as defined by the federal government. One of the findings in the report shows that “again this year, “State of the Air” finds that the burden of living with unhealthy air is not shared equally. Although people of color are 41% of the overall population of the U.S., they are 54% of the nearly 120 million people living in counties with at least one failing grade.” Bexar County received an F (failing).

High ozone levels can be dangerous to both human health and the environment. Ozone is a gas composed of three oxygen atoms (O3) and is a major component of smog. While ozone in the stratosphere plays a crucial role in protecting us from harmful ultraviolet radiation, ground-level ozone is a pollutant.

Exposure to high levels of ground-level ozone can have several adverse effects on human health, including:

  1. Respiratory Issues: Ozone can irritate and inflame the respiratory system, leading to coughing, throat irritation, chest discomfort, and worsened asthma symptoms. Prolonged exposure can damage lung tissue and increase the risk of respiratory infections.
  2. Reduced Lung Function: Ozone can decrease lung function, particularly in individuals with pre-existing respiratory conditions, such as asthma, chronic obstructive pulmonary disease (COPD), or bronchitis.
  3. Cardiovascular Effects: Ozone exposure can lead to cardiovascular problems, including heart attacks, strokes, and an increased risk of premature death, particularly in susceptible individuals.
  4. Increased Susceptibility to Other Health Issues: Ozone exposure can make individuals more susceptible to other respiratory infections, allergies, and pulmonary diseases.

Trees play a crucial role in mitigating the dangers of high ozone levels through a process called phytoremediation. Here’s how trees can help:

  1. Ozone Absorption: Trees can absorb ozone through the stomata (tiny openings) on their leaves. The ozone is then broken down into oxygen and stored within the tree.
  2. Air Quality Improvement: Trees act as natural air filters, removing pollutants from the atmosphere, including ozone and other harmful gases. They help reduce the overall concentration of ozone in the air.
  3. Shade and Cooling Effect: Trees provide shade, which can help reduce temperatures in urban areas. High temperatures contribute to the formation of ground-level ozone, so shading can indirectly mitigate ozone formation.
  4. Particulate Matter Removal: Trees also capture and remove particulate matter from the air, which can interact with ozone and exacerbate its harmful effects.
  5. Ecosystem Health: By improving air quality, trees contribute to the overall health of ecosystems, including the health of other plant and animal species.

However, it’s important to note that while trees can help mitigate ozone dangers, they are not a complete solution. Reducing the emissions of ozone precursors, such as nitrogen oxides (NOx) and volatile organic compounds (VOCs), is crucial to effectively combatting high ozone levels. Combining efforts to reduce emissions and increasing tree cover can have a synergistic effect in improving air quality and reducing ozone-related risks.

With the continued deforestation throughout Bexar County due to development, extreme weather events, and drought, expanding and preserving our tree canopy is more important now than ever before. To learn how to help your trees survive the predicted hotter and drier summer than normal, please check out this video from the Texas Forest Service: Tree Watering Tips – How to Properly Water your Trees. To learn more about any water restrictions in your area, please visit the SAWS Drought Restriction & Watering Rules or the Bexar County Water Control and Improvement District websites for more information. We can all do our part to be a responsible part of the solution. Thank you for all you do!

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